A significant patient concern in mammography and breast tomosynthesis is the discomfort the patient may feel when the breast is compressed, typically between two rigid plastic surfaces, with sufficient force to immobilize the breast and spread out the breast tissues for x-ray imaging. Another significant challenge is to ensure that the imaged field include the desired amount of breast tissue. The reasons for using compression include: (1) to make the breast thinner in the direction of x-ray flux and thereby reduce patient radiation exposure from the level required to image the thicker parts of a breast that is not compressed; (2) to make the breast more uniform in thickness in the direction of x-ray flux and thereby facilitate more uniform exposure at the image plane over the entire breast image; (3) to immobilize the breast during the x-ray exposure and thereby reduce image blurring; and (4) to bring breast tissues out from the chest wall into the imaging exposure field and thus image more tissue. As the breast is being compressed, typically a technician manipulates the breast to position it appropriately and counter the tendency that compression has of pushing breast tissue toward the chest wall and out of the image field.
Standard compression methods for mammography and tomosyntesis use a movable, rigid clear plastic compression paddle. The breast is placed on a breast platform that typically is flat, and the paddle is then compressed onto the breast, usually while a technician or other health professional is holding the breast in place and perhaps manipulates the breast to ensure proper tissue coverage in the image receptor's field of view and to help spread the breast.
One reason for discomfort that the patient may feel is that the compression force is non-uniformly distributed throughout the breast. It is concentrated at the thickest portion of the breast, usually near the chest wall, at or near the lower front edge of the compression paddle and the upper front corner of the breast platform. The anterior portion of the breast, such as near the nipple, may receive less compressive force, or no compression force. The paddle may not even contact this portion of the breast. (The terms front, lower and upper pertain to using a CC imaging orientation, with the patient facing the front of the imaging system, although it should be understood that other imaging orientations, including MLO, are used with the same equipment and these terms need to be adjusted accordingly.)
Some systems improve patient comfort by providing compression paddles that tilt as the breast is being compressed. A tilting paddle arrangement is available in various paddle sizes from Lorad of Danbury, Conn., a division of the assignee hereof, Hologic, Inc. of Bedford, Mass., under the trade name F.A.S.T. (of FAST). This tilting paddle provides more uniform compression across the breast, and more comfortable breast examinations.
Other methods for improving patient comfort have been proposed and some have been in clinical use to improve patient comfort. One is the use of relatively thin foam pads that are placed above and/or below the breast. The pad deforms to some extent during the compression procedure and may provide improved comfort by spreading out the pressure to a greater extent than using a hard-surfaced paddle and/or breast platform alone. One such pad system is discussed in commonly owned U.S. Pat. Nos. 6,968,033, 6,765,984, 6,577,702, and 7,505,555, and published U.S. patent application US 2003/0007597 A1. Another pad system is proposed in U.S. Pat. Nos. 6,850,590 and 6,975,701 and published U.S. patent applications US 2006/0050844 A1, US 2004.0156472 A1 and US 2003/0099325 A1, all naming as the inventor Benjamin M. Galkin Such pads are not transparent to visible light. As a result, if such a pad is between the breast and the compression paddle, the breast will not be visible through the paddle, and this can impair the technician's effort to position and manipulate the breast during compression. The pad needs to be made of fairly dense thin form, so as to provide meaningful deformability when compressed under or above the breast. If the foam pad slips during positioning and as a result does not cover the entire imaging field, an edge of the pad may cause image artifacts.
Another system for improving patient comfort has been proposed for a different purpose—to immobilize the breast during biopsy—by Scientific Biopsy (www.sbiopsy.com). It is understood to use a soft, trough-shaped support to cradle the breast and a flexible band that wraps over the breast to impose a holding force. A thin plastic sheet compressing a breast for ultrasound examination rather than for x-ray imaging is proposed in published patent application US 2003/0007598 A1 (see, e.g., FIG. 7 and paragraph [0115]) but no teaching could be found that the material is transparent to visible light or that the arrangement is useful for x-ray imaging or with a flat breast platform. U.S. Pat. No. 6,682,484 discusses the use of a polymeric membrane stretched under tension to restrain the breast during sonographic and/or x-ray imaging. U.S. Pat. No. 7,822,457 discusses the use of tensioned membrane to compress the breast for medical imaging, and that the membrane may be tensioned with a mechanical device or by means of an inflatable bladder. U.S. Pat. No. 6,587,578 discusses a non-rigid object holder comprising a resilient membrane attached to a first member to form an inflatable component for holding the object to be examined between the inflatable component and a base support.
Commonly assigned U.S. Pat. Nos. 7,489,761 and 7,792,244 describe (1) placing a fluid-filled pillow or bag between the compression paddle and the breast before the breast is compressed, (2) compressing the breast with a sheet of a material such as Mylar stretched or at least supported between two rods or rollers (instead of using a conventional compression paddle), and (3) using a paddle provided with a lining of concave compressible material.
All of the patents and applications identified above are hereby incorporated by reference in this patent specification as though they are fully set forth herein.
While at least some of the systems mentioned above are believed to have advantageous features, it is believed that a need still remains to further improve breast imaging and patient comfort. This patent specification is directed to new approaches to address challenges in breast imaging and particularly x-ray breast imaging.
One non-limiting example of such new approaches in mammography and/or breast tomosynthesis involves the use of a specially adapted device to control, distribute and re-direct breast compression forces. Preferably, the device comprises an inflatable jacket for the compression paddle.
In a non-limiting example, an x-ray breast imaging system that uses the new approach comprises a data acquisition unit in which an x-ray source selectively emits an imaging x-ray beam, an image receptor receives the beam and produces x-ray imaging information in response thereto, and a breast immobilizer that is between the source and the receptor. The immobilizer comprises a breast platform configured to support a patient's breast for imaging with said beam and a compression paddle supported for movement toward the breast platform to compress the breast and away from the breast platform to release the breast. The compression paddle has a front wall configured to be adjacent the patient's chest wall when the patient's breast is supported for imaging, side walls extending transversely to the front wall, and an underside facing the breast platform. A paddle jacket is removably secured to the compression paddle. Typically, the jacket has a double thickness bottom that extends along the underside of the paddle when secured to the paddle and forms an inflatable chamber. A fluid conduit extends from the chamber to a device to inflate the chamber. Typically, there is a quick-attach coupling between the conduit and the chamber, so that the chamber can be in fluid-flow communication with a fluid control unit that selectively supples fluid to the chamber to selectively inflate the chamber. An image processor coupled with the image receptor is configured to receive imaging information and produce x-ray images. A workstation and system control unit is configured to control system operations thereof in response to operator inputs.
The compression paddle jacket typically has front and side walls extending along the front and side walls of the compression paddle, respectively, and can be releasably secured to the compression paddle in any one of a number of different ways. In one example, one or more of the jacket's front and side walls comprise clipping members configured to releasably clip upper portions of one or more of the front and side walls of the compression paddle. In another example, the jacket's bottom and, if desired, the front and side walls as well, adhesively adhere to the compression paddle. An exterior portion of one or more of the front wall and bottom of said jacket can include a friction-enhancing surface configured to enhance friction with the patient's skin. The friction enhancing surface can comprise a surface with a sticky substance therein or thereon.
The jacket bottom preferably is substantially transparent to visible light, whereby a technician adjusting a patient's breast for imaging can visualize the breast through said jacket. A non-limiting example of jacket material is vinyl. The jacket bottom can include markings of a material that attenuates the x-ray beam sufficiently to make the markings visible or at least detectable in said x-ray images. The jacket's inflatable chamber in divided into two or more sub-chambers that are inflatable to different pressures. In one example, the jacket can be made of two layers of flexible sheet material that are seamed at least at a portion that extends along a junction between the front wall and the underside of the compression paddle.
In one example of breast imaging, a technician secures the inflatable jacket to the compression paddle and makes a connection between the jacket chamber and a fluid conduit. With the patient's breast on the breast platform, the technician lowers the paddle to compress the breast while manipulating breast tissue, and inflates the jacket's chamber to a pressure that achieves a desired compression and spreading of breast tissue. The immobilized breast is imaged in the desired imaging mode. Typically, a new paddle jacket is used for each patient, so the technician disconnects the fluid flow connection and disposes of the used jacket. The inflation and deflation can be operator-powered, such as by a hand or foot operated pump, with appropriate operator-controlled valves, or powered under operator control using suitable electric or other pumps controlled by buttons or other interface devices or under computer control triggered by the operator or by positioning the paddle relative to the breast (e.g., inflating when the paddle has reached a certain position or acts on the breast with w certain force).